1. Field of the Invention
The present invention relates to a process cartridge for use in image forming apparatus, such as imaging cartridges and toner cartridges, which is mounted in an apparatus body of an image forming apparatus such as copiers and printers. The invention further relates to an image forming apparatus having such a process cartridge for image forming apparatus mounted in an apparatus body thereof. Particularly, a feature of the invention resides in a process cartridge for image forming apparatus, which is equipped with a chip including a rewritable non-volatile memory, the process cartridge designed to effectively prevent cartridge identification information, such as toner color information, from being mistakenly rewritten, the cartridge identification information stored in the non-volatile memory and used for determining on the suitability of the cartridge.
2. Description of the Related Art
The image forming apparatuses such as the copiers and printers, conventionally employ the process cartridges for image forming apparatus, such as the imaging cartridges and toner cartridges, which contain toners therein and which are removably mounted in the apparatus bodies.
Such a process cartridge for image forming apparatus is generally equipped with the chip including the rewritable non-volatile memory such as a flash memory. This non-volatile memory stores: the cartridge identification information, such as the toner color information, used for determining on the suitability of the cartridge; operation history information indicating the condition of toner consumption and the like. A main CPU disposed in the apparatus body communicates with the chip mounted in the process cartridge for image forming apparatus so as to determine on the suitability of the process cartridge for image forming apparatus mounted in the apparatus body, to update the operation history information indicating the condition of toner consumption and the like (see, for example, Japanese Unexamined Patent Publications No. 2001-222192, No. 2002-169429 and No. 2002-258692).
However, the conventional process cartridges for image forming apparatus have the following problems. The cartridge identification information, such as the toner color information, used for determining on the suitability of the cartridge is generally stored in the same rewritable non-volatile memory as that stores the operation history information indicating the condition of toner consumption and the like. Thus, the memory permits such cartridge identification information to be easily rewritten. This leads to the problem that the cartridge identification information stored in the non-volatile memory is overwritten with erroneous cartridge identification information so that the process cartridge fails to accomplish a proper image formation.
As disclosed in Japanese Unexamined Patent Publication No. H8 (1996)-129628), the following technique has been proposed in the art. An information recording medium comprises an IC card equipped with three types of memories including a ROM, a RAM and an EEPROM, and with a CPU for accessing each of the memories. In order to prevent erroneous data from being written to the EEPROM to destruct necessary data, a CPU operation code for reading out data from EEPROM is stored in the ROM, whereas an operation code for writing data to the EEPROM is included in a write command sent from an external apparatus making a write request as needed and the write command is loaded into the RAM so that a program may be executed on the RAM.
However, the aforesaid information recording medium comprising the above IC card must store a program for executing the process of writing data to the RAM. Hence, the RAM must have such a large capacity that the RAM becomes disproportionately expensive as a memory mounted in the process cartridge for image forming apparatus. There are other problems. In a case where the program stored in the information recoding medium is changed, the above operation command included in the write command of the external apparatus must be also changed.